EXCHANGE 


Compound  Formation  in  Phenol- 
Cresol  Mixtures 


DISSERTATION 

SUBMITTED     IN    PARTIAL    FULFILMENT    OF    THE    REQUIRE- 

MENTS  FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY 

IN  THE  FACULTY  OF  PURE  SCIENCE  IN 

COLUMBIA  UNIVERSITY 


BY 

JACOB  J.  BEAVER,  B.S.,  M.A. 

New  York  City 
1921. 


The  Jackson  Press,  Kingston 
1921 


Compound   Formation   in  Phenol- 
Cresol  Mixtures 


DISSERTATION 

Submitted  in  partial  fulfillment  of  the  requirements  for  the  degree 

of  Doctor  of  Philosophy  in  the  Faculty  of  Pure  Science, 

Columbia  University 

BY 

JACOB  J.  BEAVER,  B.S.,  M.A. 
i/ 

New  York  City 
1921 


The  Jackson  Press,  Kingston 
1921 


To 
W.  J.  S. 


ACKNOWLEDGMENT 

The  author  wishes  to  thank  Professor  James  Kendall,  at  whose 
suggestion  this  problem  was  undertaken,  for  his  generous  and 
helpful  advice  and  to  express  his  appreciation  of  him  both  as  a 
friend  and  as  a  teacher. 

The  author  also  desires  to  thank  the  other  members  of  the 
chemistry  department  of  Columbia  University  for  the  many  cour- 
tesies extended  to  him. 


£51723 


COMPOUND  FORMATION  IN  PHENOL-CRESOL 
MIXTURES 

1.  What  was  attempted? 

(1)  The  attempt  was  made  to  harmonize  the  results  for  phenol- 
cresol  mixtures  with  the  general  rules  previously  formulated  with 
respect  to  addition  compound  formation  in  two  component  systems. 
The  six  binary  systems  formed  by  phenol  and  the  three  cresols  were 
examined    by    means  of  conductivity,  viscosity  and  freezing-point 
depression  measurements. 

2.  In  how  far  were  the  attempts  successful? 

(2)  It  has  been  shown  that,  in  the  systems  studied,  the  com- 
plexes formed  are  of  the  nature  of  substitution  compounds  (rather 
than  addition  compounds)   of  which  the  average  molecular    com- 
plexity, as  demonstrated  by  the  specific  conductivity,  viscosity  and 
freezing-point  depression  results,  is  not  greatly  different  from  the 
pure  components.     Under  this  view  the  observed  experimental  re- 
sults fall  into  line  with  the  general  theory  of  compound  formation. 

3.  What  contribution  actually  new  to  the  science  of  chemistry  has 
been  made? 

(3a)  New  standards  of  purity  have  been  established  and  more 
accurate  determinations  of  their  chief  physical  constants  made  for 
phenol  and  the  cresols. 

(3b)  New  and  exact  measurements  of  the  specific  conductivi- 
ties and  viscosities  of  the  six  binary  systems  formed  by  phenol  and 
the  cresols  have  been  made.  The  freezing-point  depression  curves 
for  the  pure  components  and  various  binary  mixtures  in  benzene 
solution  have  also  been  constructed. 

(3c)  Additional  confirmation  has  been  given  to  a  previously 
formulated  and  generalized  theory  of  compound  formation. 


COMPOUND  FORMATION  IN  PHENOL-CRESOL 
MIXTURES. 

In  a  series  of  communications  in  the  past  few  years1  addition 
compound  formation  in  a  large  number  of  binary  systems  has  been 
investigated,  particular  attention  being  paid  to  variations  in  the 
extent  of  compound  formation  as  the  constituent  radicals  of  the 
components  were  varied.  In  all  more  than  100  new  compounds 
have  been  isolated  and  simple  and  definite  rules  regarding  the  rela- 
tive stability  of  addition  compounds  in  solutions  have  been  derived. 
It  has  been  shown  that  the  extent  of  addition  compound  formation 
in  binary  mixtures  is  controlled  primarily  by  the  "chemical  con- 
trast," with  the  stability  of  complexes  increasing  uniformly  with  the 
differences  in  character  (i.e.,  the  positive  or  negative  nature  of  the 
constituent  groups)  of  the  two  compounds. 

In  the  course  of  the  work,  however,  it  was  noted  that  the  re- 
sults obtained  with  phenols  were  abnormal.  For  example,  it  was 
found2  that  phenol  and  the  three  cresols  gave  more  stable  compounds 
with  the  basic  substance,  dimethylyprone,  than  did  dinitrophenol  or 
even  picric  acid,  both  of  which  substances  are  more  acidic  than  the 
phenols.  It  was  further  found3  that  weak  acids,  although  of  far 
greater  acidic  strength  than  the  phenols  (as  shown  by  the  dissocia- 
tion constants),  give  the  more  stable  compounds  with  trichloracetic 
acid.  To  explain  this  discrepancy  a  tentative  explanation,  postulat- 
ing the  existence  of  phenols  in  two  tautomeric  forms  of  widely 
different  acidic  strengths,  was  proposed.1 

Recently,  Dawson  and  Mountford2  have  made  a  thorough  inves- 
tigation of  compound  formation  in  systems  of  the  type  phenol- 
cresol  by  the  freezing-point  method.  They  found  that  of  the  six 
binary  systems  possible,  five  give  evidence  of  compound  formation, 
while  the  sixth  (phenol — o-cresol)  exhibits  formation  of  solid  solu- 
tions. This  result  they  considered  as  rather  remarkable  in  view  of 
the  close  chemical  similarity  of  the  components  and  concluded  that 

iRendall,  J.A.C.S.,  36,  1222,  1722  (1914) ;  S8,  1309  (1906) ;  Kendall 
and  Carpenter  Ibid.,  36,  248  9(1914) ;  Kendall  and  Booge,  Ibid.,  38,  1712 
(1916) ;  89,  2323  (1917) ;  Kendall,  Booge  and  Andrews,  Ibid.,  39,  2303 
(1917).  

2Kendall  J.A.CS..,  36,  1222  (1910). 

3Kendall,  Ibid.,  38,  1317  (1916). 

Kendall,  Booge  and  Andrews,  J.A.C.S.,  39,  2306  (1917). 

2Jour.  Chem.  Soc.,  113,  923   (1918). 


"the  relations  disclosed  by  the  freezing-point  diagrams  are  conse- 
quently not  in  accord  with  what  would  have  been  anticipated  on 
the  basis  of  the  views  advocated  by  Kendall."  The  fact  that  the 
uniform  abnormality  of  the  phenols  had  already  been  emphasized 
was  apparently  overlooked. 

A  similar  study  of  phenol-cresol  systems  by  Fox  and  Barker3 
gave  widely  different  results,  a  stable  compound  (phenol — m-cresol) 
being  isolated  in  only  one  of  the  six  binary  systems  examined.  Four 
of  the  systems  show  eutectic  points  at  approximately  50  molecular 
per  cent  of  the  components  while  the  remaining  system  o-cresol — 
m-cresol  gives  two  eutectic  points  with  no  well-define.d  maximum 
between  them.  These  discrepancies  are  in  all  probability  due  to  the 
inadequate  purification  of  the  materials  employed  by  Fox  and  Barker 
and  to  the  general  inferiority  of  their  method.  In  view  of  the 
greater  care  exercised  by  Dawson  and  Mountford  in  all  the  details 
of  their  work,  there  is  no  reason  to  doubt  the  accuracy  of  their 
experimental  data. 

In  order  to  obtain  more  experimental  data  as  to  the  nature  of 
the  compounds  indicated  by  Dawson  and  Mountford,  and  in  the  hope 
of  bringing  the  results  for  systems  containing  phenols  into  line  with 
the  rest  of  the  previous  work,  these  six  systems  have  been  subjected 
to  additional  examination. 

CONDUCTIVITY  MEASUREMENTS 

Kendall  and  Gross1  have  shown  the  validity  of  the  general  rule 
that  compound  formation  and  ionization  in  solutions  proceed  in 
parallel.  For  a  series  of  binary  organic  mixtures  it  has  been  estab- 
lished experimentally  that  an  increase  in  compound  formation  is 
regularly  accompanied  by  a  similar  increase  in  specific  conductivity. 
Where  the  extent  of  compound  formation  was  known  to  be  very 
small  (as  shown  by  freezing-point  curves  of  the  systems),  the  con- 
ductivity was  practically  zero ;  as  compound  formation  increased  in 
amount  the  conductivity  became  measurable ;  where  combination  was 
extensive,  the  conductivity  was  very  markedly  increased,  being  in 
some  cases  over  one  hundred  times  that  of  the  higher  component. 

With  these  facts  in  mind  it  was  decided  that  the  first  line  of 
attack  in  the  present  work  was  to  be  the  determination  of  the  specific 


3J.  Soc.  Chem.  Ind.,  37,  268   (1918). 
1J.A.C.S.,  48,  (1921). 


—7— 

conductivity-composition  curves  of  the  phenol-cresol  mixtures.  As 
the  conductivities  to  be  measured  were  equal  to,  or  below,  the  order 
of  pure  water  (5.5  x  10~8  at  25 °C.)  it  was  necessary  to  have  a  cell 
with  a  much  larger  electrode  surface  than  any  available  in  order  to 
obtain  the  required  degree  of  accuracy  in  the  experimental  results. 
The  problem  was  further  complicated  by  the  necessity  of  having 
the  cell  as  small  as  possible  so  that  only  the  minimum  amount  of 
substance  would  be  used. 

To  fulfil  these  requirements  a  cell  was  constructed  using  the 
design  described  by  Beans  and  Eastlack1  but  having  six  concentric 
platinum  cylinders  for  the  electrodes  instead  of  two  as  used  by  them. 
The  electrodes  were  2\  cm.  high  with  the  smallest  cylinder  1  cm. 
in  diameter  and  the  others  increasing  in  diameter  in  steps  of  two 
millimeters  which  gives  the  outer  cylinder  a  diameter  of  2  cm. 
Alternate  cylinders  were  connected  to  heavy  platinum  wires  sealed 
into  the  supporting  tubes.  The  cylinders  are  separated  by  small 
glass  beads  attached  to  thin  glass  rods  running  through  holes  at  both 
top  and  bottom  of  the  cylinders.  There  are  three  equally  spaced 
(i.e.,  at  intervals  of  120°)  rods  at  both  ends  of  the  cylinders.  The 
three  lower  rods  are  bent  downward  and  continued  so  that  they  can 
be  sealed  into  the  bottom  of  the  cell.  This  method  of  holding  the 
electrodes  in  place  is  different  from  that  used  by  Beans  and  East- 
lack  but  was  found  to  be  necessary  in  order  to  hold  the  cylinders 
rigidly  in  place.  This  rigidity  is  a  necessity  if  a  permanent  value 
for  the  cell  constant  is  desired.  That  this  end  was  attained  is  shown 
by  the  following  results  for  the  value  of  the  cell  constant:  at  the 
beginning  of  the  work  it  was  0.001426;  six  months  later  it  was 
0.001427,  a  change  of  only  0.07  per  cent  (in  each  case  the  results 
are  the  average  of  ten  determinations).  With  this  cell  all  the  solu- 
tions, with  the  exception  of  o-cresol,  gave  a  resistance  of  less  than 
100,000  ohms,  and  no  difficulty  was  experienced  in  obtaining  dis- 
tinct minima.  Platinized  electrodes  could  not  be  used,  since  in  the 
presence  of  platinum  black  phenol-cresol  mixtures  turn  yellow,  with 
a  measurable  increase  in  conductivity.  Taylor  and  Acree2  show 
that  if  the  electrodes  are  sand  blasted  to  insure  a  rough  surface,  the 
conductivities  obtained  with  unplatinized  are  not  measurably  differ- 
ent from  those  obtained  with  platinized  electrodes.  The  electrodes 
used  in  the  above  cell  were  accordingly  sand-blasted,  and  in  that  con- 


iJ.A.C.S.,  37,  2674  (1915). 
2J.A.C.S.,  38,  2396   (1916). 


dition  exerted  no  action  on  the  solutions  but  gave  perfectly  definite 
and  consistent  readings. 

The  bridge  employed  was  a  4.7  meter  circular  slide  wire  instru- 
ment, well  grounded  and  carefully  calibrated.  The  resistance  coils 
up  to  1000  ohms  were  bifilar  wound ;  those  over  1000  ohms  were  of 
the  Curtis  type  which  have  practically  no  inductance  or  capacity 
when  using  a  1000  cycle  alternating  current.  The  capacity  of  the 
cell  was  balanced  out  by  means  of  rotary  air  condenser  connected 
in  parallel  with  the  resistance  coils.  The  source  of  current  was  a 
Vreeland  oscillator  producing  a  pure  sine  wave  alternating  current 
of  1000  cycles  per  second.  A  high  resistance  telephone  receiver  was 
used  to  determine  the  balance  point. 

Most  of  the  measurements  were  carried  out  in  a  large  Freas 
thermostat,  regulated  to  25°  ±0.005°.  The  absolute  temperature 
was  taken  from  a  thermometer  graduated  in  hundredths  of  a  degree 
and  standardized  at  the  Bureau  of  Standards.  Many  of  the  solu- 
tions which  have  a  higher  freezing-point  than  25°  could  be  super- 
cooled sufficiently  to  enable  direct  determinations  at  this  temperature 
to  be  made.  With  phenol  and  mixtures  very  rich  in  phenol,  how- 
ever, solidification  could  not  be  prevented  in  the  presence  of  the 
sand-blasted  electrodes,  although  viscosity  measurements  at  25° 
could  be  made.  To  complete  the  specific  conductivity  curves  for 
phenol-cresol  mixtures  at  25°  it  was  therefore  necessary  to  perform 
experiments  for  these  concentrations  at  higher  tempraturs  and  ex- 
trapolate the  results.1  For  this  purpose  two  smaller  thermostats, 
regulated  to  40°±0.05°  and  50°±0.10°  respectively,  were  fitted  up. 
Linear  extrapolation  was  assumed  to  be  valid  over  the  small  tem- 
perature range  involved.  While  this  assumption  is  probably  not 
strictly  accurate  the  values  so  obtained  show  very  good  agreement 
with  the  direct  measurements  at  25°,  as  may  be  seen  by  referring 
to  curves  4,  5,  6  in  figure  I.  In  this  diagram,  the  extrapolated  sec- 
tions of  the  different  curves  are  indicated  by  broken  lines. 

Mixtures  were  made  up  by  direct  weighing  with  the  use  of  a 
Lunge  pipet.  The  compositions  as  given  in  the  tables  below  are 
accurate  to  within  ±0.05  per  cent.  The  specific  conductivity  values 
are  relatively  of  the  order  of  0.1  per  cent  but  no  claim  is  made  for 
this  accuracy  in  the  absolute  values.  This  is  due  to  inductance  and 
capacity  effects  between  the  apparatus  and  earth,  when  large  resist- 

iCompare  Kendall  and  Gross,  loc.  cit.,  p.  . . 


— 9— 

ances  are  measured  by  the  use  of  a  high  frequency  alternating  cur- 
rent. 

PURIFICATION  OF  MATERIALS 

As  in  the  work  of  Kendall  and  Gross  it  was  found  that  the 
presence  of  impurities  in  quantities  insufficient  to  exert  a  measur- 
able effect  on  the  freezing-point  or  boiling-point  caused  a  very  con- 
siderable change  in  specific  conductivity.  A  constant  value  for  spe- 
cific conductivity  was  therefore  made  the  final  criterion  of  purity. 

The  method  of  purification  was  essentially  the  same  in  each 
case.  The  purest  material  obtainable  was  repeatedly  fractionated 
from  special  stills  made  of  Pyrex  glass.  The  stills  were  so  con- 
structed that  the  hot  vapors  came  in  contact  with  nothing  but  glass, 
thus  eliminating  the  possibility  of  contamination  from  the  cork.  A 
middle  fraction  of  constant  freezing-point  usually  gave  a  product 
of  constant  specific  conductivity  after  3  to  6  additional  fractiona- 
tions.1  In  view  of  the  hygroscopic  nature  of  the  materials  used  and 
of  the  marked  influence  exerted  by  traces  of  water  upon  their  spe- 
cific conductivity,  measurements  were  restricted  to  cold  dry  days. 
The  sensitivity  of  the  materials  toward  moisture  constitutes  the  chief 
source  of  error  in  the  whole  of  the  experimental  work  and  all  pos- 
sible precautions  were  taken  to  eliminate  its  effect  upon  the  results. 

THE  SYSTEM :  PHENOL— O-CRESOL 

A  c.p.  sample  of  phenol,  after  about  twenty  fractional  distilla- 
tions using  only  the  middle  fraction  in  each  succeeding  distillation, 
gave  a  final  product  of  specific  conductivity  11.98  x  10~8  at  40°  and 
14.07  x  10"8  at  SO0.1  The  only  previously  recorded  value  is  that  of 
Riesenfeld;  43  x  lO"8  at  43°.2  The  freezing-point  of  this  sample 
was  39.70±0.02°  using  a  standardized  thermometer.  This  is  iden- 
tical with  that  found  by  Morgan  and  Egloff3  for  a  specially  prepared 
and  purified  sample  of  phenol.  Several  investigators  have  reported 
considerably  higher  values  for  phenol,4  which  seems  to  indicate  that 

llt  was  found  that  the  addition  of  0.2  grams  of  anhydrous  sodium 
carbonate  to  100  grams  of  phenol  hastened  the  elimination  of  impurities. 

irrhe  fact  that  twenty  fractionations  were  required  to  purify  the 
material  shows  how  difficult  it  is  to  remove  the  last  traces  of  impurities. 
On  the  average  100  grams  of  purified  material  was  obtained  from  1000 
grams  of  the  crude  material. 

2Riesenfeld,  Z.  physik.  Chem.,  41,  346  (1902). 

3J.A.C.S.,  38,  844  (1916). 

442.4°  was  found  for  a  Kahlbaum  sample  (Kendall  and  Carpenter, 
J.A.C.S.,  86,  2498  (1914). 


—10— 

the  commercial  product  is  apt  to  contain  some  impurity  which  raises 
its  freezing-point.  The  original  material  here  employed  gave  a 
slightly  higher  freezing-point  than  that  of  the  final  product. 

Pure  o-cresol  was  obtained  from  a  c.p.  product  by  similar  con- 
tinued fractionation,  the  final  material  possessing  a  specific  con- 
ductivity of  0.127  x  10-8  at  25°  and  a  freezing-point  of  30.60±0.02°. 
No  previous  measurements  of  the  conductivity  are  recorded;  for 
the  freezing-point  the  highest  recorded  value  is  30.45 °.1 

The  data  for  this  system  are  given  below  in  Table  1.  The 
compositions  of  the  solutions  are  expressed  in  molecular  per  cent 
throughout.  The  specific  conductivities  are  in  reciprocal  ohms  x  10s 
at  25°  except  as  noted  above.  The  viscosity  data  which  are  added 
will  be  discussed  later. 

TABLE  I 
PHENOL  -  O-CRESOL 

Mol.  %  Phenol           Spec.  Cond.  x  108  Viscosity 

0,0  0.127  0.07608 

13.43  0.375  0.07835 

19.73  0.415  0.07930 

30.00  0.612  0.08099 

38.81  0.693  0.08235 

49.10  0.885  0.08404 

62.83  1.686  0/08565 

69.27  2.583  0.08645 

75.79  3.321  0.08731 

80.03  4.196  0.08757 

87.30  5.422  0.08825 

90.10  6.183  0.08851 

100.00  8.84  0.08945 

THE  SYSTEM:  PHENOL— M-CRESOL 

Pure  m-cresol  was  prepared  by  repeated  fractionation  of  a  c.p. 
sample.  The  effect  of  the  distillation  over  sodium  carbonate  in  low- 
ering the  specific  conductivity  was  very  marked  in  the  case  of  this 
substance.  The  specific  conductivity  of  the  final  product  was 
1.397  x  10-8  at  25°;  its  freezing-point  was  11.10±0.02°.  The 
freezing-point  as  reported1  is  10.9° ;  no  conductivity  measurements 
could  be  found. 


1Dawson  and  Mountford,  loc.  cit. 

iRendall,  J.A.C.S.,  88,  1315  (1916).  Dawson  and  .Mountford  em- 
ployed a  product  freezing  at  10.0°;  Fox  and  Barker  used  material  with 
a  much  lower  freezing-point,  their  material  apparently  containing  about 
15  per  cent,  p-cresol.  (See  Dawson  and  Mountford  ,loc.  cit.,  p.  924). 


—11— 

TABLE  II 
PHENOL  -  M-CRESOL 

Mol.  %  Cresol  Spec.  Cond.  x  10s  Viscosity 

0.0  8.84  0.08945 

6.99  7.431  0.09105 

10.79  6.810  0.09206 

18.10  5.923  0.09398 

26.75  5.094  0.09698 

36.48  4.197  0.09961 

48.26  3.379  0.1040 

54.98  2.988  0.1070 

61.52  2.587  0.1095 

68.63  2.175  0.1131 

75.51  1.887  0.1169 

87.41  1.592  0.1250 

100.00  1.397  0.1342 

THE  SYSTEM :  PHENOL— P-CRESOL 

The  preparation  of  pure  p-cresol  from  several  presumedly  c.p. 
samples  was  unsuccessfully  attempted,  the  elimination  of  traces  of 
m-cresol  (which  possess  almost  exactly  the  same  boiling-point)1  not 
being  possible.  To  obtain  pure  p-cresol  pure  p-toluidine(F.P.  43.0°) 
was  diazotized  in  6  molar  hydrochloric  acid  solution  by  slow  addition 
of  the  theoretical  amount  of  sodium  nitrite,  the  temperature  being 
maintained  below  10°  and  thorough  mixture  secured  by  vigorous 
stirring.  When  the  reaction  was  complete,  the  temperature  was 
gradually  raised  to  40°  and  the  solution  allowed  to  stand  over  night. 
It  was  then  steam  distilled,  the  distillate  extracted  with  ether,  dried 
and  fractionated  as  described  above.  The  specific  conductivity  of 
the  material  used  was  1.378  x  10~8  at  25° ;  it  gave  a  freezing-point 
of  34.55 ±0.02°.  Practically  the  same  freezing-point  was  obtained 
by  Kendall  and  Carpenter2  and  Kendall3;  while  the  material  used 
by  Dawson  and  Mountford  possessed  a  freezing-point  of  34.15°. 
No  previous  determination  of  specific  conductivities  are  recorded  in 
the  literature. 

It  was  found  that  no  matter  how  carefully  the  para  isomer  was 
purified  it  turned  yellow  in  the  course  of  a  day  if  exposed  to  sun- 
light. The  other  pure  substances  when  purified  as  outlined  above 
would  show  no  appreciable  color  at  the  end  of  a  month.  As  there 

1The  b.p.  (under  760  mm.  pressure)  of  m-cresol  is  202.1°,  of  p-cresol 
202.5°.  In  the  cases  of  phenol  and  p-cresol  or  phenol  and  o-cresol  the 
differences  in  b.p.  are  sufficient  to  permit  of  their  separation  by  fractiona- 
tion.  (See  Dawson  and  Mountford,  loc.  cit.,  p.  937). 

2Kendall  and  Carpenter,  loc.  cit. 

'Kendall,  J.A.C.S.,  88,  1315  (1916). 


—12— 

was  no  detectable  impurity  present  it  is  probable  that  the  para  com- 
pound is  considerably  more  sensitive  to  light  than  its  homologues. 
The  data  presented  below  in  Table  III  were  obtained  with  the  use 
of  freshly-prepared  material. 


TABLE  III 
PHENOL  -  P-CRESOL 

Mol.  %  Cresol  Spec.  Cond.  x  108  Viscosity 

0.08945 
0.09463 
0.09835 
0.1042 
0.1099 
0.1175 
0.1218 
0.1327 
0.1474 

SYSTEMS  CONTAINING  TWO  CRESOLS 

In  Tables  IV,  V  and  VI  below,  the  conductivity  and  viscosity 
results  for  the  binary  cresol  mixtures  are  given. 

TABLE  IV 


.  %  Cresol 

Spec.  Cond.  x 

108 

0.0 

8.84 

12.17 

7.151 

24.13 

5.863 

36.15 

4.972 

47.82 

4.201 

61.49 

3.423 

68.09 

3.012 

84.02 

2.210 

100.00 

1.378 

0-CRESOL  -  M-CRESOL 


Mol.  %  meta 

Spec.  Cond,  x  108 

0.0 

0.127 

11.97 

0.178 

23.92 

0.184 

36.29 

0.362 

49.40 

0.633 

60.46 

0.767 

64.64 

0.874 

69.39 

0.977 

84.63 

1.134 

100.00 

1.397 

Viscosity 
0.07608 
0.08086 
0.08582 
0.09208 
0.09939 
0.1050 
0.1075 
0.1109 
0.1216 
0.1342 


TABLE  V 
0-CRESOL  -  P-CRESOL 

Mol.  %  para  Spec.  Cond.  x  108  Viscosity 

0.0  0.127  0.07608 

12.50  0.188  0.08209 

24.27  0.190  0.08854 

36.96  0.344  0.09612 

47.44  0.410  0.1030 

57.67  0.507  0.1103 

64,75  0.553  0.1163 

70.91  0.601  0.1200 

84.53  0.726  0.1327 

100.00  1.378  0.1474 


—13— 


Mol.  %  para 

0.0 

8.65 

17.33 

26.27 

29.29 

32.67 

37.62 

44.79 

51.77 

54.80 

69.97 

75.39 

86.12 

100.00 


TABLE  VI 

M-CRESOL  -  P-CRESOL 
Spec.  Cond.  x  108 


397 
384 
378 
,442 
449 
,512 
,551 
,583 
,567 
,560 
.728 
,603 
,495 


1.378 


Viscosity 
0.1343 
0.1346 
0.1352 
0.1360 
0.1361 
0.1369 
0.1373 
0.1385 
0.1393 
0.1401 
0.1425 
0.1432 
0.1450 
0.1474 


The  specific  conductivity  results  given  in  the  above  tables  are 
represented  graphically  in  Figure  I.  Curves  I,  II,  III  show  the  data 
for  the  binary  cresol  systems,  curves  IV,  V,  VI  the  data  for  mix- 
tures of  phenol  with  cresols. 


2-0 


t-0 


I.METAr-PARA-C  R£$OL 

H.ORTHO-M.E.TA  -CRJE^OI 

HLORTHO-PARA-fc  RE  SOL, 


I , 


I ,  m  MOIi*  PA£A-CR£$OLr-*-  CURVE 


EL  PHE/  (ObORTHCX:it£5OL 


100 


—14— 

It  is  quite  evident  from  inspection  of  this  diagram  that  the  spe- 
cific conductivities  of  all  the  solutions  examined  are  very  little 
different  from  those  of  the  pure  components.  This  type  of  curve, 
according  to  the  work  of  Kendall  and  Gross,1  is  characteristic  of  all 
mixtures  in  which  the  two  components  are  essentially  similar  in 
character.  In  such  mixtures  little  or  no  increase  in  molecular  com- 
plexity through  compound  formation  is  to  be  expected.  Hence  the 
observed  conductivity  of  such  solutions  should  not  differ  to  a  marked 
extent  (if  the  parallelism  between  molecular  complexity  and  ioniza- 
tion  is  accepted)  from  that  obtained  by  linear  extrapolation  from 
the  specific  conductivities  of  its  constituents. 

The  conductivity  results  obtained  are  therefore  in  apparent  con- 
tradiction with  the  freezing-point  results  of  Dawson  and  Mountford, 
and  in  agreement  with  the  generalization  previously  formulated  by 
Kendall  and  quoted  above,  (p.  1.) 

This  discrepancy  will  be  discussed  more  fully  below,  after  the 
work  on  two  other  physical  properties  of  phenol-cresol  mixtures  has 
been  described.  The  investigation  of  the  viscosity-composition 
curves  of  these  systems  was  chosen  as  the  second  line  of  attack 
because  of  the  marked  effect  of  changes  in  molecular  complexity 
upon  the  viscosity. 

VISCOSITY  MEASUREMENTS 

In  general  viscosity  curves  for  binary  liquid  mixtures  fall  into 
three  distinct  types.2  The  ideal  curve,  given  by  solutions  in  which 
no  interactions  at  all  take  place  on  mixture  is  not  linear  but  appre- 
ciably sagged.  Where  compound  formation  occurs  in  the  mixtures, 
the  viscosity  is  abnormally  high ;  if  compound  formation  is  extensive 
the  curve  may  even  exhibit  a  maximum.  These  results  are  in  har- 
mony with  the  definition  of  viscosity  as  "essentially  fractional  re- 
sistance encountered  by  molecules  of  a  solution  moving  over  one 
another"  3  and  with  the  observed  experimental  facts  as  to  the  in- 
crease of  viscosity  with  increasing  molecular  weight  in  a  homologus 
series.1  Where  dissociation  of  an  associated  component  takes  place 
on  admixture,  the  viscosity  (owing  to  the  production  of  smaller 
molecules)  is  abnormally  low;  if  the  dissociation  is  extensive  the 
curve  may  even  exhibit  a  minimum.  In  certain  cases  both  com- 

iRendall  and  Gross,  loc.  cit.,  p.  . . 

2See  Kendall  and  Munroe,  J.A.C.S.,  43,  115  (1921). 

3Kendall,  Medd.  K.  Veten.  Nobelinst.,  2,  No.  25  (1913). 


—15- 

pound  formation  and  dissociation  effects  may  be  existent  reproduc- 
ing a  curve  quite  similar  to  the  ideal  type.2  A  brief  consideration 
of  the  chemical  character  of  the  components  will  be  sufficient  to 
enable  one  to  distinguish  such  a  system  from  one  which  is  truly 
ideal.  Usually,  however,  one  effect  will  predominate  sufficiently  to 
give  a  curve  quite  distinct  from  the  normal  type. 

It  was  hoped,  therefore,  that  a  study  of  the  viscosity  curves  of 
phenol-cresol  systems  would  either  make  possible  a  decision  between 
the  apparently  conflicting  conclusions  drawn  from  freezing-point 
and  conductivity  measurements,  or  indicate  the  true  conclusions. 

The  apparatus  used  for  the  determination  of  viscosities  was  of 
the  Bingham  type3,  the  experimental  procedure  being  essentially  the 
same  as  described  by  Kendall  and  Monroe.4  The  tubes  used  were 
calibrated  by  means  of  pure  m-cresol  whose  absolute  viscosity  in 
C.G.S.  units  was  obtained  from  another  tube  previously  standardized 
by  means  of  conductivity  water.  The  viscosity  value  for  water  was 
taken  as  0.008946.  Using  this  value  the  constants  for  the  tube  are 
obtained  from  the  complete  viscosity  formula: 

t     \.iz  nPV 


(<7=aceleration  due  to  gravity  ;  r=radius  of  the  capillary  ;  F=trans- 
piration  volume;  /=total  length  of  capillary;  w=number  of  capil- 
laries; P=density  of  the  liquid),  which  reduces  to  the  form 


where  C  and  C  are  the  constants  of  the  tube. 

The  relative  accuracy  of  the  viscosity  data  given  in  Tables  I  to 
VI  above  is  ±0.2  per  cent.  With  the  apparatus  employed  a  some- 
what higher  precision  is  attainable  for  most  substances,  but  the  tem- 
perature coefficient  of  viscosity  of  the  substances  employed  is  ex- 
tremely high  —  approximately  10  per  cent  per  degree.1  Accurate 
density  values  are  not  essential  for  the  exact  determination  of  vis- 
cosity with  the  Bingham  type  of  instrument  since  the  density  enters 

iDunstan  and  Thole,  "The  Viscosity  of  Liquids,"  p.  15. 
2Compare  Kendall  and  Brakeley,  J.A.C.S.,  43,  (1921). 
3Bingham  J.  Ind.  Eng.  Chem.,  6,  233  (1914)  ;  Bingham,  Schlesinger 
and  Coleman,  J.A.C.S.,  38,  27  (1916). 

4Kendall  and  Monroe,  J.A.C.S.,  39,  1787  (1917). 
^ramley,  loc.  cit.,  p.  10. 


—16— 

into  the  working  formula  only  in  the  kinetic  energy  correction- 
factor  which  is  approximately  1  per  cent  of  the  total.  Consequently, 
after  it  had  been  found  for  each  system  that  the  density  of  an 
approximately  equimolecular  mixture  was,  within  error  limits,  iden- 
tical with  the  density  found  by  linear  interpolation  from  the  specific 
volume-weight  composition  curves,  no  other  density  values  were 
determined.2 

The  viscosity  results  for  the  six  systems  are  reproduced  in 
graphic  form  in  the  accompanying  diagram  (Figure  II).  Inspection 
of  these  curves  shows  that  they  are  all  very  near  to  the  ideal  type. 


When  it  is  remembered,  however,  that  we  have  independent 
evidence  from  other  physical  properties3  that  phenol  and  the  cresols 
are  highly  associated  liquids  it  follows  that  this  approximation  to 
the  normal  type  of  curve  must  be  due  to  the  mutual  result  of  the 

2This  assumption  is  in  agreement  with  the  actual  density  determina- 
tions carried  out  by  Fox  and  Barker  [J.  Soc.  Chem.  Ind.,  36,  845  (1917] 
with  less  pure  materials. 

3See  Turner,  "Molecular  Association";  also  data  given  later. 


—17— 

two  opposing  effects  discussed  above — compound  formation  and  dis- 
sociation. It  appears  that  neither  effect  is  predominant  here,  com- 
bination between  the  components  being  practically  counterbalanced 
by  mutual  depolymerization,  leaving  the  average  molecular  com- 
plexity essentially  unchanged. 

To  obtain  confirmation  of  this  point  of  view,  the  molecular 
weights  of  the  pure  substances,  and  the  average  molecular  weights 
of  their  binary  mixtures,  were  determined  in  an  inert  solvent. 

MOLECULAR  WEIGHT  DETERMINATIONS 

The  freezing-point  of  a  pure  liquid,  on  addition  of  an  ideal 
solute,  will  be  depressed  according  to  the  equation  i1 

lnx=(-Q/RT0}  .  (AT/T) 

(where  x  is  the  molecular  fraction  of  solvent  in  the  solution;  Q  the 
molecular  heat  of  fusion  of  the  solvent ;  T0  and  T  the  absolute  freez- 
ing-points of  the  pure  solvent  and  the  solution  respectively ;  AT  the 
freezing-point  depression;  and  R  1.9852).  If  the  solute  is  not  ideal 
but  associated,  its  average  molecular  weight  in  any  solution  of  known 
composition  can  be  calculated  from  the  above  equation  by  substi- 
tuting the  experimentally  determined  value  for  T  and  solving  for  x. 

Benzene  was  selected  as  a  suitable  ideal  solvent.  The  ideal 
freezing-point  depression  curve  for  this  liquid  has  been  given  in  a 
previous  article.2  The  benzene  used  in  the  present  work  was  dried 
over  sodium  and  carefully  fractionated  from  the  same  substance. 
The  fraction  used  distilled  between  80.2°— 80.3°.  (corr.) 

To  determine  the  freezing-point  depression  of  benzene  on  addi- 
tion of  phenol  and  the  cresols  the  standard  Beckmann  apparatus  and 
method  were  employed  using  a  thermometer  calibrated  at  the  Bureau 
of  Standards.  Undercooling  was  limited  to  0.1°  to  0.2°.  For  the 
depressions  tabulated  in  Table  VII  the  accuracy  claimed  is  0.01°. 
The  "compound  mixtures"  were  obtained  by  weighing  somewhere 
near  the  approximate  amounts  of  the  two  components  into  a  small 
flask  and  then  adding  small  amount  of  one  of  the  components  until 
the  desired  composition  was  obtained.  In  all  cases  the  molecular  com- 
position is  within  0.1  per  cent  of  the  theoretical  molecular  composi- 
tion of  the  compound. 

iRoozeboom,  "Heterogene  Gleichgewichte",  2,  273    (1904). 
2Kendall  and  Monroe,  J.A.C.S.,  43,  115  (1921). 


—18— 


TABLE  VII 
FREEZING-POINT  DEPRESSION  DATA 


Phenol 

Mol.  %  Solute  AT 

0.97  0.398° 

1.81  0.711° 

3.17  1.190° 

4.50  1.621° 

6.38  2.221° 

7.92  2.635° 


Mol. 


Ortho-Cresol 


%  o-cresol 
0.88 
1.86 
2.84 
3.81 
4.71 
5.95 
7.53 


AT 

0.591° 
1.170° 
1.752° 
2.257° 
2.728° 
3.341° 
4.082° 


Meta-Cresol 


Para-Cresol 


Mol. 

%  m-cresol 

AT 

0.67 

0.434° 

1.54 

0.925° 

2.00 

1.161° 

3.10 

1.711° 

4.33 

2.161° 

5.43 

2.584° 

6.01 

2.843° 

7.72 

3.424° 

1  Phenol :  2  m-Cresol 


33.33  mol.  % 
Mol.%  compound 

0.66 

1.71 

2.78 

4.04 

5.70 

7.25 

8.70 
10.24 
11.74 


66.67  mol. 
AT 

0.380° 
0.908° 
1.396° 
1.905° 
2.490° 
2.987° 
3.409° 
3.890° 
4.347° 


Mol.  %  para 

AT 

0.95 

0.590° 

2.01 

1.180° 

3.18 

1.691° 

4.54 

2.225° 

5.70 

2.625° 

7.10 

3.102° 

8.68 

3.569° 

10.33 

4.065° 

1  Phenol: 

1  o-Cresol 

49.90  mol.  %  : 

50.10  mol.  % 

Mol.%  compound 

AT 

1.15 

0.602° 

2.33 

1.180° 

3.64 

1.774° 

5.07 

2.383° 

6.65 

2.998° 

7.79 

3.444° 

9.46 


4.060' 


2  Para:  1  Ortho 
66.71  mol.  %  :  33.29  mol.  % 
Mol.  %  compound  AT 

0.91 
2.02 
3.02 
4.11 
5.34 
6.72 
8.59 


0.590° 
1.218° 
1.727° 
2.239° 
2.743° 
3.275° 
3.953° 


The  freezing-point  depression  data  for  three  of  the  systems 
(those  for  o-cresol,  phenol  and  for  an  equimolecular  mixture  of 
phenol  and  o-cresol)  are  shown  graphically  in  Figure  III.  The 
abnormally  small  depressions  obtained  for  phenol  show  that  this 


—19— 

substance  is  extensively  associated.  The  curve  for  o-cresol,  on  the 
other  hand,  is  very  much  closer  to  the  ideal  curve,  indicating  that  it 
is  much  less  associated  than  phenol.  The  equimolecular  mixture 
gives  a  curve  which  falls  practically  midway  between  those  of  its 
two  components.  This  indicates  that  the  average  molecular  com- 


Fic;» EL 


I.  IDEAL, 
H.ORTHOCRESOL 


J2.PHfiNOL 


\.\. 


2-0 


M.OL% 


40.0 


4-O 


plexity  of  the  mixture  is  of  the  same  order  as  that  of  the  pure  sub- 
stances. 

Exactly  the  same  result  is  obtained  from  the  other  data  given 
in  Table  VII  above.  Each  of  the  two  mixtures  tested  (phenol  and 
m-cresol  in  molecular  proportion  I  to  2;  o-cresol  and  p-cresol  in  the 
molecular  proportion  1  to  2)  corresponds  to  a  definite  compound 
isolated  by  Dawson  and  Mountford.  In  each  case  the  freezing-point 
depression  curve  for  the  compound  mixture  falls  intermediate  be- 
tween the  curves  for  the  respective  components,  and  nearer  to  that 
component  in  which  the  mixture  is  richer. 

If  these  phenol-cresol  compounds  were  true  addition  compounds 
(their  formation  involving  an  increase  in  molecular  complexity)  en- 


—20— 

tirely  different  results  would  have  been  obtained.  Although  the 
dissociation  of  such  compounds  into  their  simpler  components  would 
be  favored  by  the  dilution  of  the  mixture  with  a  large  excess  of 
solvent  benzene  we  should  still  find  appreciable  combination  indi- 
cated by  abnormally  small  freezing-point  depressions.  Thus,  to  give 
an  example,  it  has  been  found1  that  the  freezing-point  depression  of 
a  solution  of  ethyl  acetate  in  benzene  is  practically  unchanged  on 
the  addition  of  an  equimolecular  amount  of  trichloracetic  acid,2 
showing  that  the  acid-ester  addition  compound  formed  is  only 
slightly  broken  up  into  its  components  in  benzene  solution.  Ethyl 
acetate  and  acetic  acid  give  a  similar,  but  much  less  decided  increase 
in  molecular  complexity  when  mixed  in  benzene  solution.  In  the 
system  containing  phenol  and  the  cresols,  however,  the  freezing- 
point  depression  curves  resemble  the  viscosity  curves  in  showing 
practically  no  change  in  molecular  complexity ;  any  compound  forma- 
tion between  the  components  must  therefore  be  compensated  for  by 
simultaneous  depolymerization. 

In  order  to  supply  a  definite  idea  as  to  the  relative  molecular 
complexities  in  the  different  solutions  examined,  the  following  table 
is  given.  As  an  arbitrary  concentration  for  comparing  the  different 
systems,  5  molecular  per  cent  has  been  chosen.  The  added  specific 
conductivity  and  viscosity  data  will  be  discussed  later. 

TABLE  VIII 

ASSOCIATION  OF  PHENOL,  ETC.,  IN  BENZENE  SOLUTION 
Solute  concentration— 5  molecular  per  cent. 

AT       Mol.Wt.  AvgMol.  Spec.Cond.  Viscosity 
Complex-    x  108  at  25°     at  25° 

ity 

phenol  1.780°  178.4  1.897  8.84  0.08945 

o-cresol  2.861°  125.1  1.157  0.127  0.07608 

m-cresol  2.450°  146.9  1.358  1.397  0.1342 

p-cresol   2.400°  150.2  1.390  1.378  0.1474 

1  phenol +  1  o-cresol   ..2.342°  144.5  1.427  0.979  0.08415 

1  phenol +  2  m-cresol  ..   2.258°  153.2  1.482  2.230  0.1121 

1  o-cresol +2  p-cresol. .   2.613°  137.6  1.274  0.570  0.1177 

The  results  given  above  are  in  good  agreement  with  those  of 
previous  investigators3  in  indicating  that  phenol  is  much  more  highly 

Unpublished  data  obtained  by  Dr.  J.  E.  Booge  in  this  laboratory. 

'Kendall  and  Booge,  J.A.C.S.,  88,  1712  (1916)  show  that  the  two 
substances  form  a  stable  equimolecular  addition  compound  freezing  at 
—27.5°. 

3Beckmann,  Z.  physik.  Chem.,  2,  715  (1888) ;  Aurvers,  Ibid.,  12,  689 
(1893);  Mascarelli  and  Benati,  Gazz.  chim.  ital.,  37,  527  (1907);  39  B, 
642  (1909) ;  Hewitt  and  Winmill,  J.  Chem.  Soc.,  91,  441  (1907). 


—21— 

associated  than  the  cresols.  The  specific  conductivity  of  phenol,  it 
will  be  noted,  is  also  considerably  greater  than  the  values  obtained 
for  the  cresols — a  fact  in  exact  accordance  with  the  work  of  Kendall 
and  Gross2  in  which  a  parallelism  between  specific  conductivity  and 
molecular  complexity  in  a  series  of  liquids  of  similar  type  was  pre- 
dicted. 

O-cresol  is  much  less  associated  than  its  two  isomers,  for  which 
the  association  factors,  like  their  other  physical  properties,  are  quite 
similar.  As  was  to  be  expected  from  their  greater  association  the 
specific  conductivities  of  m-cresol  and  p-cresol  are  much  higher 
than  that  for  o-cresol.  The  influence  of  this  association  factor  is 
also  evident  in  the  relative  viscosity  values. 

GENERAL  CONCLUSIONS 

The  following  experimental  facts  have  been  established  with 
regard  to  phenol-cresol  mixtures :  (a)  Dawson  and  Mountford  have 
isolated  compounds  in  five  of  the  six  possible  binary  systems  by  the 
freezing-point  method,  (b)  the  specific  conductivity-composition 
curves  show  no  significant  divergence  from  the  normal  curves,  (c) 
the  viscosity-composition  curves  are  all  "pseudo-ideal"  in  type,  (d) 
the  freezing-depression  curves  (which  are  also  relative  molecular 
weight  curves)  given  by  binary  mixtures  in  benzene  solution  fall 
intermediate  between  the  curves  found  for  the  pure  components. 
As  noted  above  the  conclusions  drawn  from  these  facts  are  not  in 
harmony  with  one  another.  It  now  remains  to  be  seen  if  a  rational 
explanation  can  be  given  which  will  harmonize  these  results  with 
the  general  hypothesis  correlating  chemical  contrast,  compound 
formation  and  conductivity  in  solution  developed  by  Kendall  and 
his  co-workers,  or  whether  the  whole  behavior  of  systems  containing 
phenols  must  continue  to  be  classed  as  "abnormal." 

A  careful  consideration  of  the  problem  shows  that  an  extension 
to  these  solutions  of  the  views  presented  by  Kendall  and  Gross 
(loc.  cit.,  p.  .  .)  regarding  conductivity  and  molecular  complexity  in 
pure  associated  liquids,  and  binary  mixtures  of  the  same,  supplies  a 
complete  explanation  of  the  points  in  dispute. 

Phenol  and  the  cresols,  as  already  shown,  are  highly  associated 
in  the  liquid  state.  The  association  of  phenol,  in  particular,  has  been 
critically  investigated  by  several  investigators,1  the  conclusions 

2Loc.  cit. 

1Yamnaoto,  Sakuri  Memorial  Papers,  Article  12,  p.  33  (1908)  ; 
Mascarelli  and  Benati,  loc.  cit. ;  Beckmann  and  .Maxim,  Z.  physik.  Chem., 
89,  411  (1914). 


—22— 

reached  being  that  the  main  equilibrium  is  represented  by  the  equa- 
tion: 

3(C6H5OH)^(C6H5OH)3. 

Some  investigators2  postulate  the  existence  of  still  more  complex 
molecular  types  of  phenol. 

Now  it  has  been  noted  by  Kendall  and  Gross  that  in  a  solution 
containing  two  highly  associated  components  of  similar  character, 
compounds  of  the  general  type  (AB)X  .  (CD)y  are  undoubtedly 
formed  in  quantity.  The  average  molecular  complexity  of  such  a 
mixture,  however,  (and  hence  its  specific  conductivity  also)  will  not 
differ  greatly  from  that  of  its  pure  components  since  disassociation 
of  these  is  also  involved.  The  complexes  here'  existent  are  to  be 
regarded  not  as  addition  but  rather  as  substitution  compounds,  for 
disintegration  and  recombination  of  the  various  molecular  and  ionic 
types  present  will  finally  result  in  an  almost  "haphazard"  replace- 
ment of  the  different  radicals  by  one  another  at  all  points  of  the 
original  molecules  (AB)  and  (CD).  If  the  attractive  forces  be- 
tween the  constituent  groups  are  such  that  at  a  certain  pafticular 
substitution  complex  is  predominantly  stable,  then  it  is  only  logical 
to  expect  that  such  a  complex  may  be  definitely  isolated  under  suit- 
able conditions  (e.g.,  by  freezing  the  solution).  The  phenol-cresol 
compounds  described  by  Dawson  and  Mountford  are  consequently 
not  true  addition  compounds  as  the  physical  properties  given  above 
sufficiently  demonstrate,  but  substitution  compounds  formed  by  the 
replacement  of  part  of  an  associated  molecule  by  part  of  a  different 
associated  molecule.  It  is  very  significant  that  all  five  of  the  com- 
pounds isolated  by  the  freezing-point  method  are  trimolecular,  e.g., 
2  m-cresol+1  phenol,  2  p-cresol-fl  phenol.  Such  complexes  could 
be  readily  formed  from  the  predominating  phenol  complex 
(C6H5OH)3  by  replacement  of  two  phenol  groups.  No  increase  in 
the  average  molecular  complexity  of  the  mixture  is  involved  in  such 
replacements,  and  the  apparent  contradiction  between  Dawson  and 
Mountford's  results  and  those  of  the  present  work  is  therefore  re- 
moved. 

It  must  also  be  noted  that  mixtures  of  this  type,  if  no  particular 
substitution  complex  predominates  in  stability,  will  necessarily  tend 
to  give  "mixed  crystals"  on  solidification,  as  in  the  case  of  the 
phenol  -  o-cresol  system.  Analogous  behavior  is  shown  by  binary 

2Mascarelli  and  Benati,  loc.  cit. 


—23— 

mixtures  of  fused  salts  of  similar  character,  e.g.,  neutral  salts  of 
the  alkali  metals.1  Thus  potassium  sulfate  gives  a  continuous  series 
of  solid  solutions  with  sodium  sulfate  and  also  with  potassium  chro- 
mate.  Lithium  sulfate  and  potassium  fluoride,  on  the  other  hand, 
form  stable  equimolecular  compounds  with  potassium  sulfate.  These 
latter  systems  are  evidentally  identical  in  character  with  the  five 
compound-producing  phenol-cresol  mixtures. 

SUMMARY 

By  repeated  f ractionation,  very  pure  samples  of  phenol  and  the 
three  cresols  have  been  prepared,  and  their  chief  physical  constants 
determined.  The  specific  conductivity  and  viscosity  curves  for  the 
different  systems  have  been  carefully  determined.  Freezing-point 
depression  curves  for  phenol,  the  cresols,  and  various  binary  mix- 
tures in  benzene  solution  have  also  been  constructed.  Without 
exception,  the  results  indicate  that  no  increase  in  molecular  complex- 
ity occurs  in  the  different  systems.  This  is  in  agreement  with  the 
views  correlating  addition  compound  formation  with  diversity  in 
character  of  the  components  previously  formulated  by  Kendall  and 
his  co-workers,  but  apparently  in  disagreement  with  the  fact  that  in 
five  of  the  six  systems  definite  compounds  were  isolated  by  Dawson 
and  Mountford. 

A  brief  consideration  of  the  equilibria  existent  in  binary  mix- 
tures of  associated  liquids  has  shown  that  the  compounds  present  in 
these  systems  are  to  be  regarded  as  substitution  rather  than  as  addi- 
tion compounds.  Under  this  view  the  results  of  Dawson  and 
Mountford  and  those  of  the  present  work  fall  directly  into  line  with 
the  general  theory. 


iLandolt-Bornstein,  Tabellen,  1912,  p.  611-37. 


—24— 


VITA 

Jacob  J.  Beaver  was  born  in  Schenectady,  N.Y.,  on  February 
23,  1893,  attending  the  grade  and  high  schools  of  that  city.  He 
received  the  degree  of  B.S.  from  Union  University  in  June,  1915. 
From  September,  1915,  until  June,  1917,  he  attended  the  graduate 
school  of  Columbia  University,  receiving  the  degree  of  M.A.  in 
June,  1916.  From  June,  1917,  until  he  resumed  his  studies  at 
Columbia  he  was  in  the  government  service.  In  1919  he  was 
laboratory  assistant  in  physical  chemistry,  in  1920  Goldschmidt 
Fellow  in  Chemistry  and  in  1921  lecturer  in  chemistry  in  Columbia. 


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